Methods and systems for generating polyols

ABSTRACT

Disclosed are methods for generating propylene glycol, ethylene glycol and other polyols, diols, ketones, aldehydes, carboxylic acids and alcohols from biomass using hydrogen produced from the biomass. The methods involve reacting a portion of an aqueous stream of a biomass feedstock solution over a catalyst under aqueous phase reforming conditions to produce hydrogen, and then reacting the hydrogen and the aqueous feedstock solution over a catalyst to produce propylene glycol, ethylene glycal and the other polyols, diols, ketones, aldehydes, carboxylic acids and alcohols. The disclosed methods can be run at lower temperatures and pressures, and allows for the production of oxygenated hydrocarbons without the need for hydrogen from an external source.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/800,671 filed May 7, 2007, which claimed the benefit of U.S.provisional application 60/798,484 filed May 8, 2006. Each applicationis incorporated herein by reference in its entirety.

FEDERAL FUNDING STATEMENT

This invention was made with United States government support awarded byDOC NIST Grant No 70NANB3H3014 and DOE Grant No. DE-FG36-05GO15046. TheUnited States has certain rights in this invention.

TECHNICAL FIELD

The present invention is directed to methods, catalysts and reactorsystems for generating one or more oxygenated hydrocarbon products froman aqueous feedstock stream containing a water-soluble oxygenatedhydrocarbon. Preferably, the reaction products include diols and otherpolyols, ketones, aldehydes, carboxylic acids and/or alcohols producedby hydrogenating water-soluble polyols (such as glycerol) in abiomass-derived feedstock using hydrogen produced within a reactorsystem from a portion of the biomass feedstock stream.

BACKGROUND

Biomass (material derived from living or recently living biologicalmaterials) is becoming one of the most important renewable energyresources. The ability to convert biomass to fuels, chemicals, energyand other materials is expected to strengthen rural economies, decreasedependence on oil and gas resources, and reduce air and water pollution.The generation of energy and chemicals from renewable resources such asbiomass also reduces the net rate of carbon dioxide production, animportant greenhouse gas that contributes to global warming.

A key challenge for promoting and sustaining the use of biomass in theindustrial sector is the need to develop efficient and environmentallybenign technologies for converting biomass to useful products. Presentbiomass conversion technologies unfortunately tend to carry additionalcosts which make it difficult to compete with products produced throughthe use of traditional resources, such as fossil fuels. Such costs ofteninclude capital expenditures on equipment and processing systems capableof sustaining extreme temperatures and high pressures, and the necessaryoperating costs of heating fuels and reaction products, such asfermentation organisms, enzymatic materials, catalysts and otherreaction chemicals.

One alternative fuel technology receiving significant attention isbiodiesel produced via the esterification of vegetable oils or animalfats. The US production of biodiesel is reaching 30-40 million gallonsannually, but is projected to grow to a targeted 400 million gallons ofproduction per year by 2012. In Europe, over 1.4 metric tons ofbiodiesel was produced in 2003, and major initiatives are underway inBrazil and Asia.

A byproduct of the biodiesel process is crude glycerol, which has littleor no value without further refinement. The issue is what to do with theescalating supply of crude glycerol. Purification of crude glycerol isone option, however, the refining of crude glycerol, which containscatalyst, organic impurities and residual methanol, is difficult andoften too expensive for small scale biodiesel producers. To complicatematters, the demand for pure glycerol has also remained static andprices have dropped dramatically as more supply is brought on line,especially in Europe.

The development of effective methods to convert crude glycerol toalternative products, such as diols and other polyols, ketones,aldehydes, carboxylic acids and alcohols, may provide additionalopportunities to improve the cost effectiveness and environmentalbenefits of biodiesel production. For example, over a billion pounds ofpropylene glycol is produced in the United States today and used in themanufacture of many industrial products and consumer products, includingaircraft and runway deicing fluids, antifreeze, coolants, heat transferfluids, solvents, flavors and fragrances, cosmetic additives,pharmaceuticals, hydraulic fluids, chemical intermediates, and inthermoset plastics. Propylene glycol is currently produced via thepartial oxidation of fossil fuel derived propylene to form propyleneoxide, which is then reacted with water to form propylene glycol.

Researchers have recently developed methods to react pure hydrogen withlarger biomass-derived polyols (glycerol, xylitol, and sorbitol) andsugars (xylose and glucose) over hydrogenation and hydrogenolysiscatalytic materials to generate propylene glycol. While the biomass isderived from a renewable source, the pure hydrogen itself is generallyderived through the steam reforming of non-renewable natural gas. Due toits origin, the pure hydrogen must also be transported to and introducedinto the production stream at elevated pressures from an externalsource, thereby decreasing the efficiency of the process and causing anincrease in the overall cost of the ultimate end-product.

For instance, U.S. Pat. Nos. 6,841,085, 6,677,385 and 6,479,713 to Werpyet al., disclose methods for the hydrogenolysis of both carbon-oxygenand carbon-carbon bonds using a rhenium (Re)-containing multimetalliccatalyst in the presence of external hydrogen to produce products suchas propylene glycol (PG). The Re-containing catalyst may also includeNi, Pd, Ru, Co, Ag, Au, Rh, Pt, Ir, Os and Cu. The conversion takesplace at temperatures in a range from 140° C. to 250° C., and morepreferably 170° C. to 220° C., and a hydrogen pressure between 600 psito 1600 psi hydrogen.

Dasari et al. also disclose hydrogenolysis of glycerol to PG in thepresence of hydrogen from an external source, at temperatures in a rangefrom 150° C. to 260° C. and a hydrogen pressure of 200 psi, over nickel,palladium, platinum, copper and copper-chromite catalysts. The authorsreported increased yields of propylene glycol with decreasing waterconcentrations, and decreasing PG selectivity at temperatures above 200°C. and hydrogen pressures of 200 psi. The authors further reported thatnickel, ruthenium and palladium were not very effective forhydrogenating glycerol. Dasari, M. A.; Kiatsimkul, P.-P.; Sutterlin, W.R.; Suppes, G. J. Low-pressure hydrogenolysis of glycerol to propyleneglycol Applied Catalysis, A: General, 281(1-2), p. 225 (2005).

U.S. patent application Ser. No. 11/088,603 (Pub. No. US2005/0244312 A1)to Suppes et al., disclose a process for converting glycerin into loweralcohols having boiling pointes less than 200° C., at high yields. Theprocess involves the conversion of natural glycerin to propylene glycolthrough an acetol intermediate at temperatures from 150° C. to 250° C.,at a pressure ranging from 1 to 25 bar (14.5 to 363 psi), and preferablyfrom 5 to 8 bar (72.5 to 116 psi), over a palladium, nickel, rhodium,zinc, copper, or chromium catalyst. The reaction occurs in the presenceor absence of hydrogen, with the hydrogen provided by an externalsource. The glycerin is reacted in solution containing 50% or less byweight water, and preferably only 5% to 15% water by weight.

SUMMARY

The present invention is directed to methods for generating oxygenatedhydrocarbons, such as polyols, diols, ketones, aldehydes, carboxylicacids and alcohols, from an aqueous feedstock solution using hydrogenproduced from a portion of the feedstock solution. The method involvesthe reaction of a portion of the feedstock solution over a firstcatalyst under aqueous phase reforming conditions to produce hydrogen,and reacting the hydrogen with at least a second portion of thefeedstock solution over a second catalyst under conditions appropriateto produce the desired products (e.g., by hydrogenation). In oneembodiment, the method includes the steps of (a) contacting a firstcatalytic material with an aqueous feedstock solution containing waterand at least one water soluble oxygenated hydrocarbon having two or morecarbon atoms to produce hydrogen, and (b) reacting the hydrogen with theremaining oxygenated hydrocarbons over a second catalytic materialselected to promote the hydrogenation of the oxygenated hydrocarbons tothe desired reactant products.

The aqueous feedstock solution preferably includes water and anoxygenated hydrocarbon having at least two carbon atoms, such as any oneof a number of polyols, sugars, sugar alcohols, alcohols, starches,lignins, cellulosics and water soluble saccharides. Preferably, thefeedstock solution includes glycerol.

The first catalytic material is desirably a heterogeneous catalysthaving one or more materials capable of producing hydrogen under aqueousphase reforming conditions, such as Group VIIIB metals, whether alone orin combination with Group VIIB metals, Group VIB metals, Group VBmetals, Group IVB metals, Group JIB metals, Group IB metals, Group IVAmetals, or Group VA metals. The second catalytic material is preferablya heterogeneous catalyst having one or more materials capable ofcatalyzing a reaction between the generated hydrogen and the feedstocksolution to produce diols or other polyols, ketones, aldehydes,carboxylic acids and/or alcohols. Preferred examples of the secondcatalytic material include copper Group VIII metals, mixtures and alloysthereof, and various bifunctional catalysts. The second catalyticmaterial may include these metals alone or in combination with one ormore Group VIIIB, VIIB metals, Group VIB metals, Group VB metals, GroupIVB metals, Group IIB metals, Group IB metals, Group WA metals, or GroupVA metals. Preferably, the second catalytic material includes iron,ruthenium, copper, rhenium, cobalt or nickel.

In one embodiment, polyols, diols, ketones, aldehydes, carboxylic acidsand/or alcohols are generated by producing hydrogen from a portion ofthe aqueous feedstock solution placed in contact with a first catalyticmaterial at a temperature from about 80° C. to 400° C., a weight hourlyspace velocity (WHSV) of at least about 1.0 gram of oxygenatedhydrocarbon per gram of first catalytic material per hour and a pressurewhere the water and the oxygenated hydrocarbons are condensed liquids,and then reacting the hydrogen with a second portion of the feedstocksolution over a second catalytic material under conditions oftemperature, pressure and weight hourly space velocity effective toproduce one or more oxygenated hydrocarbons, such as diols and otherpolyols, ketones, aldehydes, carboxylic acids and/or alcohols. Thesecond portion of the feedstock solution will generally include bothoriginal oxygenated hydrocarbons and oxygenated hydrocarbons resultingfrom the hydrogen production step, and may be contacted with the secondcatalytic material at a temperature from about 100° C. to 300° C., apressure from about 200 psig to about 1200 psig and a weight hourlyspace velocity of at least about 1.0 gram of oxygenated hydrocarbon pergram of catalytic material per hour per hour. The resulting compositionmay generally include, without limitation, a multiphase composition ofmatter having a solid phase with a catalyst composition containing thefirst catalytic material and the second catalytic material, preferablyplatinum and iron, and a fluid phase containing water, glycerol,carboxylic acid, propylene glycol and carbon dioxide.

In another embodiment, reactor systems are provided for producingoxygenated compounds, such as diols or other polyols, ketones,aledhydes, carboxylic acids and/or alcohols, from a polyol. The reactorsystem includes at least a first reactor bed adapted to receive anaqueous feedstock solution to produce hydrogen and a second reactor bedadapted to produce the oxygenated compounds from the hydrogen and aportion of the feedstock solution. The first reactor bed is configuredto contact the aqueous feedstock solution in a condensed phase with afirst catalytic material (described above) to provide hydrogen in areactant stream. The second reactor bed is configured to receive thereactant stream for contact with a second catalytic material (describedabove) and production of the desired oxygenated compounds. In onepreferred embodiment, the first catalytic material includes a Group VIIImetal, while the second catalytic material is either iron, ruthenium,copper, rhenium, cobalt, nickel or alloys or mixtures thereof. Thesecond reactor bed may be positioned within the same reactor vesselalong with the first reaction bed or in a second reactor vessel incommunication with a first reactor vessel having the first reaction bed.The reactor vessel preferably includes an outlet adapted to remove theproduct stream from the reactor vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting the thermodynamics (ΔG°/RT versustemperature) for the production of CO and H₂ from vapor-phase reformingof CH₄, C₂H₆, C₃H₈ and C₆H₁₄; CH₃(OH), C₂H₄(OH)₂, C₃H₅(OH)₃ andC₆H₈(OH)₆; and water-gas shift. Dotted lines show values of ln(P) forthe vapor pressures versus temperature of CH₃(OH), C₂H₄(OH)₂, C₃H₅(OH)₃,and C₆H₈(OH)₆ (pressure in units of atm).

FIG. 2 is a reaction schematic depicting reaction pathways for theproduction of H₂ and propylene glycol from glycerol.

FIG. 3 is a reaction schematic depicting reaction pathways for theproduction of H₂ and propyl alcohol from glycerol.

FIG. 4 is a reaction schematic depicting reaction pathways for theproduction of H₂ and hexanol from sorbitol.

FIG. 5 is a schematic diagram illustrating a process for converting apolyol to a diol or alcohol using in-situ generated hydrogen.

FIG. 6 is a schematic diagram illustrating a process for generatingreaction products from a polyol using a reactor having a first reactionchamber for generating hydrogen and a second hydrogenation chamber.

FIG. 7 is a schematic diagram illustrating a process for generatingreaction products from a polyol with an added supplement using a reactorhaving a first reaction chamber for generating hydrogen and a secondhydrogenation chamber.

FIG. 8 is a schematic diagram of a reactor system that can be used toevaluate the generation of polyols from glycerol via aqueous-phasereforming; and

FIG. 9 is a graph depicting the distribution of carbon products duringaqueous phase reforming of glycerol over a modified platinum catalyst.

DETAILED DESCRIPTION

The present disclosure relates to methods and systems for reformingconcentrations of biomass with water at low temperatures to producepropylene glycol, ethylene glycol and other polyols, diols, ketones,aldehydes, carboxylic acids and/or alcohols using in-situ generatedhydrogen. The hydrogen may be generated by reacting a portion of anaqueous feedstock solution containing the biomass and water over acatalyst under aqueous phase reforming (APR) conditions. The hydrogengenerated by APR may then be used to react with a second portion of thefeedstock solution, including the oxygenated hydrocarbons derived fromthe production of the APR hydrogen, over a second catalyst underconditions appropriate to produce the desired products.

ABBREVIATIONS AND DEFINITIONS

“GC”=gas chromatograph or gas chromatography.

“GHSV”=gas hourly space velocity.

“psig”=pounds per square inch relative to atmospheric pressure (i.e.,gauge pressure).

“Space Velocity”=the mass/volume of reactant per unit of catalyst perunit of time.

“TOF”=turnover frequency.

“WHSV”=weight hourly space velocity=mass of oxygenated compound per massof catalyst per hour.

“WGS”=water-gas shift.

Aqueous-Phase Reforming (APR) is a catalytic reforming process thatgenerates hydrogen-rich fuels from oxygenated compounds derived frombiomass (glycerol, sugars, sugar alcohols, etc.). Various APR methodsand techniques are described in U.S. Pat. Nos. 6,699,457; 6,964,757 and6,964,758; and U.S. patent application Ser. No. 11;234,727 (all toCortright et al., and entitled “Low-Temperature Hydrogen Production fromOxygenated Hydrocarbons”); and U.S. Pat. No. 6,953,873 (to Cortright etal., and entitled “Low Temperature Hydrocarbon Production fromOxygenated Hydrocarbons”); and commonly owned co-pending InternationalPatent Application No. PCT/US2006/048030 (to Cortright et al., andentitled “Catalyst and Methods for Reforming Oxygenated Compounds”), allof which are incorporated herein by reference. The term “aqueous phasereforming” and “APR” shall generically denote the overall reaction of anoxygenated compound and water to yield a hydrogen stream, regardless ofwhether the reactions takes place in the gaseous phase or in thecondensed liquid phase. Where the distinction is important, it shall beso noted. “APR hydrogen” shall generically refer to the hydrogenproduced by the APR process.

The APR process is preferably performed in the liquid phase, although itmay also be carried out in a vapor phase reaction. APR can occur attemperatures where the water-gas shift reaction is favorable (e.g., 80°C. to 400° C.), making it possible to generate hydrogen with low amountsof CO in a single chemical reactor. Advantages of the APR processinclude: (i) the performance of the reaction at lower pressures(typically at 200 to 725 psig); (ii) the ability to generate ahydrogen-rich feedstock at lower temperatures without the need tovolatilize water, which provides a major energy savings; (iii) theability to operate at temperatures that minimize undesirabledecomposition reactions typically encountered when carbohydrates areheated to elevated temperatures; and (iv) the utilization ofagricultural derived feedstocks. The APR process takes advantage of theunique thermodynamic properties of oxygenated compounds having afavorable carbon-to-oxygen stoichiometry, especially hydrocarbons havinga C:O ratio of 1:1 (the preferred ratio), to generate hydrogen atrelatively low temperatures in a single reaction step.

The stoichiometric reaction for reforming an oxygenated hydrocarbonhaving a C:O ratio of 1:1 to produce CO and H₂ is given by reaction 1.

C_(n)H_(2y)O_(n)

nCO+yH₂  (1)

Reaction conditions for producing hydrogen from hydrocarbons can bedictated by the thermodynamics for the steam reforming of alkanes toform CO and H₂ (reaction 2), and the water-gas shift reaction to formCO₂ and H₂ from CO (reaction 3).

C_(n)H_(2n+2)+nH₂O

nCO+(2n+1)H₂  (2)

CO+H₂O

CO₂+H₂  (3)

FIG. 1 (constructed from thermodynamic data obtained from ChemicalProperties Handbook, C. L. Yaws, McGraw Hill, 1999) shows changes in thestandard Gibbs free energy (ΔG°/RT) associated with equation 2 for aseries of alkanes (CH₄, C₂H₆, C₃H₈, C₆H₁₄), normalized per mole of COproduced. It can be seen that the steam reforming of alkanes isthermodynamically favorable (i.e., negative values of ΔG°/RT) only attemperatures higher than 675 K (402° C.).

Relevant oxygenated hydrocarbons having a C:O ratio of 1:1, such asmethanol (CH₃OH), ethylene glycol (C₂H₄(OH)₂), glycerol (C₃H₅(OH)₃), andsorbitol (C₆H₈(OH)₆), are also illustrated. On FIG. 1, dotted lines showvalues of ln(P) for the vapor pressures versus temperature of CH₃(OH),C₂H₄(OH)₂, C₃H₅(OH)₃, and C₆H₈(OH)₆ (pressure in units of atm). FIG. 1shows that steam reforming of these oxygenated hydrocarbons to produceCO and H₂ is thermodynamically favorable at significantly lowertemperatures than those required for alkanes with similar numbers ofcarbon atoms. FIG. 1 also shows that the value of ΔG°/RT for water-gasshift of CO to CO₂ and H₂ is more favorable at similarly lowtemperatures. Consequently, it is possible to reform oxygenatedhydrocarbons with favorable C:O ratios at low-temperatures to form COand H₂, and subsequently H₂ and CO₂, in a single-step catalytic process.

While FIG. 1 shows that the conversion of oxygenated compounds in thepresence of water to H₂ and CO₂ is highly favorable at low temperatures,the subsequent reaction of H₂ and oxygenated compounds to form alkanes(C_(n)H_(2n+2)) and water is also highly favorable at low temperatures.

CO₂+4H₂

CH₄+2H₂O  (4)

In a first embodiment, methods for generating oxygenated compounds areprovided. The methods preferably include the steps of (a) contacting afirst catalytic material with a first portion of an aqueous feedstocksolution containing water and water soluble oxygenated hydrocarbons toform APR hydrogen, and (b) contacting the APR hydrogen and a secondportion of the feedstock solution over a second catalytic material toproduce a reaction product that includes, without limitation, a polyol,diol, ketone, aldehyde, carboxylic acid and/or alcohol. The secondportion of the feedstock solution preferably includes oxygenatedhydrocarbons derived from the production of the APR hydrogen in additionto oxygenated hydrocarbons included in the original feedstock solution,but may also include portions of the feedstock solution withoutoxygenated hydrocarbons generated during APR hydrogen formation. Thefirst catalytic material is preferably an aqueous phase reforming (APR)catalyst, and the second catalytic material is preferably a materialcapable of catalyzing hydrogenation reactions. Unless otherwiseindicated, any discussion of hydrogenation catalysts and APR catalystsherein are non-limiting examples of suitable catalytic materials.

As described more fully below, the more thermodynamically favoredreaction consumes APR hydrogen to yield a mixture of polyols, diols,ketones, aldehydes and/or alcohols. Under favorable conditions, theprocesses and reactor systems described below may yield a mixturepredominantly comprising one or more oxygenated compounds, such as diolsand other polyols, ketones, aldehydes, carboxylic acids and/or alcohols.For example, processes and reactor systems described herein may providea carbon containing reaction product with more than 50% of one or morepolyols, such as propylene glycol. Preferably, substantially all of theAPR hydrogen generated in-situ by the APR process is consumed during thereaction with the oxygenated hydrocarbons over the second catalyticmaterial, without the addition of pure hydrogen from an external source.

FIGS. 2, 3 and 4 show schematic representations of possible reactionpathways for the formation of both H₂ and polyols, diols, ketones andalcohols from oxygenated hydrocarbons over a metal catalyst. In general,hydrogen formation involves dehydrogenation and subsequent rearrangementsteps that form intermediates containing carbon atoms unbound to oxygenatoms. The carbohydrate first undergoes dehydrogenation to provideadsorbed intermediates, prior to cleavage of C—C or C—O bonds.Subsequent cleavage of C—C bonds leads to the formation of CO and H₂,with the CO then reacting with water to form CO₂ and H₂ by the water-gasshift (WGS) reaction. The formation of polyols, diols, ketones,carboxylic acids, aldehydes, and/or alcohols follows where the hydroxylgroups of the oxygenated hydrocarbon are removed via a dehydrationmechanism with subsequent hydrogenation with the hydrogen formed above.It's also possible to form polyols, diols, ketones and/or alcohols onthe metal catalyst by first cleaving C—O bonds in adsorbed carbohydrateintermediates. The intermediates can then be converted to the polyol,diol, ketone, carboxylic acid, aldehyde, and/or alcohol depending on thecatalyst and reaction conditions.

Feedstock Solution

The preferred feedstock includes water-soluble oxygenated hydrocarbonsderived from biomass. As used herein, the term “biomass” refers to,without limitation, organic materials produced by plants (such asleaves, roots, seeds and stalks), and microbial and animal metabolicwastes. Common sources of biomass include: (1) agricultural wastes, suchas corn stalks, straw, seed hulls, sugarcane leavings, bagasse,nutshells, and manure from cattle, poultry, and hogs; (2) woodmaterials, such as wood or bark, sawdust, timber slash, and mill scrap;(3) municipal waste, such as waste paper and yard clippings; and (4)energy crops, such as poplars, willows, switch grass, alfalfa, prairiebluestream, corn, soybean, and the like. The feedstock may be fabricatedfrom biomass by any means now known or developed in the future, or maybe simply byproducts of other processes, such as crude glycerol frombiodiesel production.

The oxygenated hydrocarbons may be any hydrocarbon having at least twocarbon atoms and at least one oxygen atom. In the preferred embodiment,the oxygenated hydrocarbon is water-soluble and has from 2 to 12 carbonatoms, and more preferably from 2 to 6 carbon atoms. The oxygenatedhydrocarbon also preferably has an oxygen-to-carbon ratio ranging from0.5:1 to 1.5:1, including ratios of 0.75:1.0, 1.0:1.0, 1.25:1.0, 1.5:1.0and other ratios there between. In the most preferred embodiment, theoxygenated hydrocarbons have an oxygen-to-carbon ratio of 1:1.Nonlimiting examples of preferred water-soluble oxygenated hydrocarbonsinclude ethanediol, ethanedione, acetic acid, propanol, propanediol,propionic acid, glycerol, glyceraldehyde, dihydroxyacetone, lactic acid,pyruvic acid, malonic acid, butanediols, butanoic acid, aldotetroses,tautaric acid, aldopentoses, aldohexoses, ketotetroses, ketopentoses,ketohexoses, alditols, sugars, sugar alcohols, cellulosics,lignocellulosics, saccharides, starches, polyols and the like. Mostpreferably, the oxygenated hydrocarbon is sugar, sugar alcohols,cellulose, saccharides and glycerol.

The oxygenated hydrocarbon is combined with water to provide an aqueousfeedstock solution having a concentration effective for causing theformation of the desired reaction products. The water may be addedeither prior to contacting the oxygenated hydrocarbon to the APRcatalyst or at the same time as contacting the oxygenated hydrocarbon tothe APR catalyst. In the preferred embodiment, the water is combinedwith the oxygenated hydrocarbon to form an aqueous solution prior tocontacting the APR catalyst for easier processing, but it is alsorecognized that the oxygenated hydrocarbon may also be placed intosolution and then supplemented with water at the time of contact withthe APR catalyst to form the aqueous feedstock solution. Preferably thebalance of the feedstock solution is water. In some embodiments, thefeedstock solution consists essentially of water, one or more oxygenatedhydrocarbons and, optionally, one or more feedstock modifiers describedherein, such as alkali or hydroxides of alkali or alkali earth salts oracids. The feedstock solution may also contain negligible amounts ofhydrogen, preferably less than about 1 bar (14.5 psi). In the preferredembodiments, hydrogen is not added to the feedstock.

The water-to-carbon ratio in the solution is preferably from about 0.5:1to about 7:1, including ratios there between such as 1:1, 2:1, 3:1, 4:1,5:1, 6:1, and any ratios there between. The feedstock solution may alsobe characterized as a solution having at least 20 weight percent of thetotal solution as an oxygenated hydrocarbon. For example, the solutionmay include one or more oxygenated hydrocarbons, with the totalconcentration of the oxygenated hydrocarbons in the solution being atleast about 20%, 30%, 40%, 50%, 60% or greater by weight, including anypercentages between, and depending on the oxygenated hydrocarbons used.More preferably the feedstock solution includes at least about 20%, 30%,40%, 50%, or 60% of glycerol by weight, including any percentagesbetween. Water-to-carbon ratios and percentages outside of the abovestated ranges are also included within the scope of this invention.

Hydrogen Production

The APR hydrogen is produced from the feedstock under aqueous phasereforming conditions. The reaction temperature and pressure arepreferably selected to maintain the feedstock in the liquid phase.However, it is recognized that temperature and pressure conditions mayalso be selected to more favorably produce hydrogen in the vapor-phase.In general, the APR reaction and subsequent hydrogenation reactionsshould be carried out at a temperature at which the thermodynamics ofthe proposed reaction are favorable. The pressure will vary with thetemperature. For condensed phase liquid reactions, the pressure withinthe reactor must be sufficient to maintain the reactants in thecondensed liquid phase at the reactor inlet.

For vapor phase reactions, the reaction should be carried out at atemperature where the vapor pressure of the oxygenated hydrocarboncompound is at least about 0.1 atm (and preferably a good deal higher),and the thermodynamics of the reaction are favorable. This temperaturewill vary depending upon the specific oxygenated hydrocarbon compoundused, but is generally in the range of from about 100° C. to about 450°C. for reactions taking place in the vapor phase, and more preferablyfrom about 100° C. to about 300° C. for vapor phase reactions.

For liquid phase reactions, the reaction temperature may be from about80° C. to about 400° C., and the reaction pressure from about 72 psig toabout 1300 psig. Preferably, the reaction temperature is between about120° C. and about 300° C., and more preferably between about 150° C. andabout 270° C. The reaction pressure is preferably between about 72 and1200 psig, or between about 145 and 1200 psig, or between about 200 and725 psig, or between about 365 and 600 psig. Because the hydrogen isproduced in-situ, the pressure is provided by a pumping mechanism thatalso drives the feedstock solution through the reactor system.

The condensed liquid phase method may also optionally be performed usinga modifier that increases the activity and/or stability of the firstand/or the second catalytic material(s) (i.e., the catalyst system). Itis preferred that the water and the oxygenated hydrocarbon are reactedat a suitable pH of from about 1.0 to about 10.0, including pH values inincrements of 0.1 and 0.05 between, and more preferably at a pH of fromabout 4.0 to about 10.0. Generally, the modifier is added to thefeedstock solution in an amount ranging from about 0.1% to about 10% byweight as compared to the total weight of the catalyst system used,although amounts outside this range are included within the presentinvention.

Alkali or alkali earth salts may also be added to the feedstock solutionto optimize the proportion of hydrogen in the reaction products.Examples of suitable water-soluble salts include one or more selectedfrom the group consisting of an alkali or an alkali earth metalhydroxide, carbonate, nitrate, or chloride salt. For example, addingalkali (basic) salts to provide a pH of about pH 4.0 to about pH 10.0can improve hydrogen selectivity of reforming reactions.

The addition of acidic compounds may also provide increased selectivityto the desired reaction products in the hydrogenation reactionsdescribed below. It is preferred that the water-soluble acid is selectedfrom the group consisting of nitrate, phosphate, sulfate, and chloridesalts, and mixtures thereof. If an optional acidic modifier is used, itis preferred that it be present in an amount sufficient to lower the pHof the aqueous feed stream to a value between about pH 1.0 and about pH4.0. Lowering the pH of a feed stream in this manner may increase theproportion of diols, polyols, ketones, carboxylic acids, aldehydes,alcohols or alkanes in the final reaction products.

In general, the reaction should be conducted under conditions where theresidence time of the feedstock solution over the APR catalyst isappropriate to generate an amount of APR hydrogen sufficient to reactwith a second portion of the feedstock solution over the hydrogenationcatalyst to provide the desired products. For example, in oneembodiment, the WHSV for the reaction may be at least about 1.0 gram ofoxygenated hydrocarbon per gram of APR catalyst, and preferably betweenabout 1.0 to 5.0 grams of oxygenated hydrocarbon per gram of APRcatalyst, and more preferably between about 1.9 to 4.0 grams ofoxygenated hydrocarbon per gram of APR catalyst.

APR Catalyst

The first catalytic material is preferably an APR catalyst, typically aheterogeneous catalyst capable of catalyzing the reaction of water andoxygenated hydrocarbons to form hydrogen under the conditions describedabove. The preferred APR catalyst includes at least one Group VIIIBtransition metal, and any alloy or mixtures thereof. Preferably, the APRcatalyst includes at least one Group VIIIB transition metal incombination with at least one second metal selected from Group VIIIB,Group VIIB, Group VIB, Group VB, Group IVB, Group IIB, Group IB, GroupIVA or Group VA metals. The preferred Group VIIB metal includes rhenium,manganese, or combinations thereof. The preferred Group VIB metalincludes chromium, molybedum, tungsten, or a combination thereof. Thepreferred Group VIIIB metals include platinum, rhodium, ruthenium,palladium, nickel, or combinations thereof.

Preferred loading of the primary Group VIIIB metal is in the range of0.25 wt % to 25 wt % on carbon, with weight percentages of 0.10% and0.05% increments between, such as 1.00%, 1.10%, 1.15%, 2.00%, 2.50%,5.00%, 10.00%, 12.50%, 15.00% and 20.00%. The preferred atomic ratio ofthe second metal is in the range of 0.25-to-1 to 10-to-1, includingratios there between, such as 0.50, 1.00, 2.50, 5.00, and 7.50-to-1.

A preferred catalyst composition is further achieved by the addition ofoxides of Group IIIB, and associated rare earth oxides. In such event,the preferred components would be oxides of either lanthanium or cerium.The preferred atomic ratio of the Group IIIB compounds to the primaryGroup VIIIB metal is in the range of 0.25-to-1 to 10-to-1, includingratios there between, such as 0.50, 1.00, 2.50, 5.00, and 7.50-to-1.

Unless otherwise specified, the recitation of an APR bimetallic catalystcomposition as “X:Y” herein, where X and Y are metals, refers to a groupof catalyst compositions comprising at least metals X and Y in anysuitable stoichoimetric combination, and optionally including othermaterials. Similarly, the recitation of a catalyst composition as“X1.0Y1.0” refers herein to a composition comprising at least metals Xand Y in a 1:1 stoichiometric molar ratio. Accordingly, particularlypreferred catalytic compositions are bimetallic metal compositionsdescribed by the formula X:Y, where X is a Group VIIIB metal and Y is aGroup VIIIB, Group VIIB, Group VIB, Group VB, Group IVB, Group IIB,Group IB, Group WA or Group VA metal. For example, the catalystsdesignated “Re:Pt” include the bimetallic catalysts Re_(1.0)Pt_(1.0) andRe_(2.5)Pt_(1.0). Furthermore, recitation of a bimetallic catalyst X:Ycan include additional materials besides X and Y, such as La or Ce. Forexample, the catalysts designated “Re:Rh” herein include catalysts suchas Re_(1.0)Rh_(1.0), Re_(1.0)Rh_(3.8), Re_(1.0)Rh_(2.0)Ce_(2.0),Re_(1.0)Rh_(1.0)Ce_(1.0), and Re_(1.0)Rh_(1.0)La_(3.0).

In preferred embodiments, the catalyst system may include a supportsuitable for suspending the catalyst in the feedstock solution. Thesupport should be one that provides a stable platform for the chosencatalyst and the reaction conditions. The support may take any formwhich is stable at the chosen reaction conditions to function at thedesired levels, and specifically stable in aqueous feedstock solutions.Such supports include, without limitation, carbon, silica,silica-alumina, alumina, zirconia, titania, ceria, vanadia and mixturesthereof. Furthermore, nanoporous supports such as zeolites, carbonnanotubes, or carbon fullerene may be utilized. Particularly usefulcatalyst systems include, without limitation, platinum supported onsilica, platinum supported on silica-alumina, platinum supported onalumina, nickel supported on silica-alumina, nickel supported onalumina, ruthenium supported on silica-alumina, ruthenium supported onalumina, palladium supported on silica-alumina, and nickel-platinumsupported on silica-alumina. In one embodiment, the APR catalyst systemis platinum on silica-alumina or silica, with the platinum being furtheralloyed or admixed with nickel, ruthenium, copper, iron or rhenium. Inanother embodiment, the APR catalyst system is nick on silica-alumina orsilica, with the nickel being further alloyed or admixed with copper,rhenium, ruthenium or iron.

One particularly preferred catalyst support is carbon, especially carbonsupports having relatively high surface areas (greater than 100 squaremeters per gram). Such carbons include activated carbon (granulated,powdered, or pelletized), activated carbon cloth, felts, or fibers,carbon nanotubes or nanohorns, carbon fullerene, high surface areacarbon honeycombs, carbon foams (reticulated carbon foams), and carbonblocks. The carbon may be produced via either chemical or steamactivation of peat, wood, lignite, coal, coconut shells, olive pits, andoil based carbon. Another preferred support is granulated activatedcarbon produced from coconuts.

The support may also be treated or modified to enhance its properties.For example, the support may be treated, as by surface-modification, tomodify surface moieties, such as hydrogen and hydroxyl. Surface hydrogenand hydroxyl groups can cause local pH variations that affect catalyticefficiency. The support may also be modified, for example, by treatingit with sulfates, phosphates, tungstenates, and silanes. For carbonsupports, the carbon may be pretreated with steam, oxygen (from air),inorganic acids or hydrogen peroxide to provide more surface oxygensites. The preferred pretreatment would be to use either oxygen orhydrogen peroxide. The pretreated carbon may also be modified by theaddition of oxides of Group IVB and Group VB. It is preferred to useoxides of titanium, vanadium, zirconia and mixtures thereof.

The APR catalyst system may be prepared using conventional methods knownto those in the art. These methods include evaporative impregnationtechniques, incipient wetting techniques, chemical vapor deposition,wash-coating, magnetron sputtering techniques, and the like. The methodchosen to fabricate the catalyst is not particularly critical to thefunction of the invention, with the proviso that different catalystswill yield different results, depending upon considerations such asoverall surface area, porosity, etc.

Oxygenated Compound Production

Various oxygenated compounds may be produced by the preferred methodsand reactor systems. For example, the reaction products may include oneor more diols or other polyols, ketones, aldehydes, carboxylic acids andalcohols derived from the reaction of the in-situ generated APR hydrogenwith a portion of the remaining feedstock solution over a secondcatalytic material, preferably a hydrogenation catalyst, underconditions of reaction temperature, reaction pressure and weight hourlyspace velocity (WHSV) effective to produce the desired reactionproducts. The temperature and pressure are preferably selected toconduct the reaction in the liquid phase. It is recognized, however,that temperature and pressure conditions may also be selected to morefavorably produce the desired products in the vapor-phase. In general,the reaction should be conducted at a temperature where thethermodynamics of the proposed reaction are favorable. The pressure willvary with the temperature and WHSV. For condensed phase liquidreactions, the pressure within the reactor must be sufficient tomaintain the reactants in the condensed liquid phase at the reactorinlet.

For liquid phase reactions, the reaction temperature may be from about100° C. to about 300° C., and the reaction pressure from about 72 psigto about 1300 psig. Preferably, the reaction temperature is betweenabout 120° C. and about 270° C., and more preferably between about 200°C. and about 270° C. The reaction pressure is preferably between about72 and 1200 psig, or between about 145 and 1200 psig, or between about200 and 725 psig, or between about 365 and 600 psig.

For vapor phase reactions, the reaction should be carried out at atemperature where the vapor pressure of the oxygenated hydrocarboncompound is at least about 0.1 atm (and preferably a good deal higher),and the thermodynamics of the reaction are favorable. This temperaturewill vary depending upon the specific oxygenated hydrocarbon compoundused, but is generally in the range of from about 100° C. to about 300°C. for vapor phase reactions.

The condensed liquid phase method of the present invention may also beperformed using a modifier that increases the activity and/or stabilityof the catalyst system. It is preferred that the water and theoxygenated hydrocarbon are reacted at a suitable pH of from about 1.0 toabout 10.0, including pH values in increments of 0.1 and 0.05 between,and more preferably at a pH of from about 4.0 to about 10.0. Generally,the modifier is added to the feedstock solution in an amount rangingfrom about 0.1% to about 10% by weight as compared to the total weightof the catalyst system used, although amounts outside this range areincluded within the present invention.

In general, the reaction should be conducted under conditions where theresidence time of the feedstock solution over the catalyst isappropriate to generate the desired products. For example, the WHSV forthe reaction may be at least about 1.0 gram of oxygenated hydrocarbonper gram of catalyst per hour, and preferably between about 1.0 to 5.0grams of oxygenated hydrocarbon per gram of catalyst per hour, and morepreferably between about 1.9 to 4.0 grams of oxygenated hydrocarbon pergram of catalyst per hour.

Hydrogenation Catalyst

The second catalytic material is preferably a heterogeneoushydrogenation catalyst capable of catalyzing the reaction of hydrogenand oxygenated hydrocarbons to produce the desired reaction products.The preferred hydrogenation catalyst may include copper or at least oneGroup VIIIB transition metal, and any alloys or mixtures thereof. Thecatalyst may also be constructed to include either copper or at leastone Group VIIIB transition metal as a first metal, and at least onesecond metal from the selection of Group VIIIB, Group VIIB, Group VIB,Group VB, Group IVB, Group IIB, Group IB, Group WA or Group VA metals.The preferred Group VIIB metal includes rhenium, manganese, orcombinations thereof. The preferred Group VIB metal includes chromium,molybedum, tungsten, or a combination thereof. The preferred Group VIIIBmetals include platinum, rhodium, ruthenium, palladium, nickel, orcombinations thereof. In one embodiment, the preferred catalyst includesiron or rhenium and at least one transition metal selected from iridium,nickel, palladium, platinum, rhodium and ruthenium. In anotherembodiment, the catalyst includes iron, rhenium and at least copper orone Group VIIIB transition metal.

The second catalytic material is preferably a hydrogenation catalystthat is different from the first catalytic material, which is preferablyan APR catalyst, or a second catalyst capable of working in parallelwith or independently of the APR catalyst. The hydrogenation catalystmay also be a bi-functional catalyst. For example, acidic supports(e.g., supports having low isoelectric points) are able to catalyzedehydration reactions of oxygenated compounds, followed by hydrogenationreactions on metallic catalyst sites in the presence of H₂, againleading to carbon atoms that are not bonded to oxygen atoms. Thebi-functional dehydration/hydrogenation pathway consumes H₂ and leads tothe subsequent formation of various polyols, diols, ketones, aldehydesand alcohols. Examples of such catalysts include tungstated zirconia,titania zirconia, sulfated zirconia, acidic alumina, silica-alumina, andheteropolyacid supports. Heteropolyacids are a class of solid-phaseacids exemplified by such species as H_(3+x)PMo_(12-x)V_(x)O₄₀,H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀, H₆P2W₁₈O₆₂, and the like. Heteropolyacids aresolid-phase acids having a well-defined local structure, the most commonof which is the tungsten-based Keggin structure. The Keggin unitcomprises a central PO₄ tetrahedron, surrounded by 12 WO₆ octahedra. Thestandard unit has a net (−3) charge, and thus requires 3 cations tosatisfy electroneutrality. If the cationic are protons, the materialfunctions as a Bronsted acid. The acidity of these compounds (as well asother physical characteristics) can be “tuned” by substituting differentmetals in place of tungsten in the Keggin structure. See, for example,Bardin et al. (1998) “Acidity of Keggin-Type HeteropolycompoundsEvaluated by Catalytic Probe Reactions, Sorption Micro-calorimetry andDensity Functional Quantum Chemical Calculations,” J. or PhysicalChemistry B, 102:10817-10825.

Similar to the APR catalyst, the hydrogenation catalyst may be adheredto a support as described above. The support may be the same support asused for the APR catalyst or a support specific to the hydrogenationcatalyst as selected for the desired reaction outcome.

Preferred loading of the copper or primary Group VIIIB metal is in therange of 0.25 wt % to 25 wt % on carbon, with weight percentages of0.10% and 0.05% increments between, such as 1.00%, 1.10%, 1.15%, 2.00%,2.50%, 5.00%, 10.00%, 12.50%, 15.00% and 20.00%. The preferred atomicratio of the second metal is in the range of 0.25-to-1 to 10-to-1,including any ratios between such as 0.50, 1.00, 2.50, 5.00, and7.50-to-1. In one embodiment, the hydrogenation catalyst includes iron(Fe), a Group VIIIB metal, with an atomic ratio of Fe to the primaryGroup VIIIB metal from 0.25-to-1 to 10-to-1. If the catalyst is adheredto a support, the combination of the catalyst and the support is from0.25 wt % to 10 wt % of the copper or primary Group VIIIB metal.

The heterogeneous catalyst may also be combined with the APR catalyst toform a mixture so as to allow the APR reaction and the hydrogenationreaction to occur simultaneously, or nearly simultaneously, in a singlereactor vessel. In such event, the recitation of a bimetallic catalystcomposition as “X:Y”, where X is an APR catalyst and Y is ahydrogenation catalyst, shall refer to a group of catalyst compositionscomprising at least APR catalyst X and hydrogenation catalyst Y, in anysuitable stoichoimetric combination and including other materials whenindicated. For example, the catalysts designated “Pt:Fe” includes themixture Pt_(1.0)Fe_(1.0) and Pt_(2.5)Fe_(1.0). Particularly preferredcatalysts include Pt_(1.0)Ni_(1.0)Fe_(1.0) and Pt_(1.0)Fe_(1.0)Cu_(1.0),where Pt and Pt:Ni represent the APR catalyst and Fe and Fe:Cu representthe hydrogenation catalyst.

The preferred atomic ratio of the APR catalyst (first catalyticmaterial) to the hydrogenation catalyst (second catalytic material) isin the range of 5:1 to 1:5, such as, without limitation, 4.5:1,4.0:1,3.5:1, 3.0:1, 2.5:1, 2.0:1, 1.5:1, 1:1, 1:1.5, 1:2.0, 1:2.5,1:3.0, 1:3.5, 1:4.0, 1:4.5, and any amounts there between. For example,in one embodiment, a catalyst mixture is provided the APR catalystincluding platinum and the hydrogenation catalyst including iron (Pt:Fe)at a ratio of 1:1. If the catalyst mixture is adhered to a support, thecombination of the catalyst and the support may be from 0.25 wt % to 10wt % of the mixture.

The hydrogenation catalyst system, whether alone or mixed with the APRcatalyst, may be prepared using conventional methods known to those inthe art. Such methods include evaporative impregnation, incipientwetting, chemical vapor deposition, wash-coating, magnetron sputteringtechniques, and the like. The method chosen to fabricate the catalyst isnot particularly critical to the function of the invention, with theproviso that different catalysts will yield different results, dependingupon considerations such as overall surface area, porosity, etc.

Reactor

The reaction system can be configured such that the flow direction ofthe aqueous feedstock solution can be selected to ensure maximalinteraction of the in-situ generated hydrogen with the feedstocksolution. For example, the reactor may be designed so that an APRcatalyst and a hydrogenation catalyst are stacked in a single reactionvessel, or separated so that the APR catalyst and hydrogenation catalystare in separate reaction vessels. The reactor may also be designed toaccommodate multiple APR catalysts and hydrogenation catalysts so as toallow for optimal production of more than one reaction product. Thereactor system may also include additional inlets to allow for theintroduction of supplemental materials to further advance or direct thereaction to the desired reaction products, and to allow for therecycling of reaction byproducts for use in the reforming process.

The reactor may be designed so that the feedstock solution flowshorizontally, vertical or diagonally to the gravitational plane so as tomaximize the efficiency of the system. In systems where the feedstocksolution flows vertically or diagonally to the gravitational plan, thefeedstock solution may flow either against gravity (up-flow system) orwith gravity (down-flow system). In one preferred embodiment, thereactor is designed as an up-flow system such that the feedstocksolution flows through the reactor in an upwards direction. In thisembodiment, the feedstock solution first contacts a first reaction bedcontaining the APR catalyst to produce APR hydrogen. Due to theconfiguration of the reactor, the APR hydrogen is then able to, undercertain conditions, percolate through a second reaction bed containingthe hydrogenation catalyst at a rate greater than or equal to thefeedstock solution to maximize the interaction of the feedstock solutionwith the hydrogen and hydrogenation catalyst.

In a reactor with a single chamber, the APR catalyst and hydrogenationcatalyst may be placed in a stacked configuration to allow the feedstocksolution to first contact the APR catalyst and then the hydrogenationcatalyst, or a series of hydrogenation catalysts depending on thedesired reaction products. The reaction beds for the APR catalyst andhydrogenation catalyst, or catalysts, may also be placed side-by-sidedependent upon the particular flow mechanism employed, such as ahorizontal flow system. In either case, the feedstock solution may beintroduced into the reaction vessel through one or more inlets, and thendirected across the catalysts for processing. In the preferredembodiment, the feedstock solution is directed across the APR catalystto produce APR hydrogen, and then both the APR hydrogen and theremaining feedstock solution are directed across the hydrogenationcatalyst, or catalysts, to produce the desired reaction products. Inembodiments employing a mixture of APR catalyst and hydrogenationcatalyst, the generation of the APR hydrogen and the reaction productsmay occur simultaneously or in parallel.

In a separate reactor configuration, the reactor may be designed toallow for APR hydrogen production to occur in a reaction bed in onereaction vessel with the reaction products generated in another reactionvessel. The reaction vessels may be configured to run in parallel orsequentially. In a parallel configuration, the feedstock solution may beseparated to direct a first portion of the feedstock solution to thehydrogen reaction bed where APR hydrogen is produced, and a secondportion to a hydrogenation reaction bed where the desired reactionproducts are produced using APR hydrogen generated by the hydrogenreaction vessel. Alternatively, the reactor may be configured toaccommodate the use of two separate feedstock solutions, with the firstfeedstock solution directed to the hydrogen reaction vessel and thesecond feedstock solution directed to the hydrogenation reaction vessel.In a sequential configuration, the reactor may be designed so that thefeedstock solution flows through the hydrogen reaction vessel and intothe hydrogenation reaction vessel. In either of these systems, becausethe APR hydrogen is produced in-situ, the pressure is provided by apumping mechanism that also drives the feedstock solution through thereactor chambers.

Supplemental Materials

Supplemental materials and compositions (“supplements”) may be added tothe feedstock solution at various stages of the process in order toenhance the reaction or to drive it to the production of the desiredreaction products. Supplements may include, without limitation, acids,salts and additional hydrogen or feedstock. Such supplements may beadded directly to the feedstock stream prior to or contiguous withcontacting the hydrogenation catalyst, or directly to the reaction bedfor the hydrogenation reaction.

In one embodiment, the supplement may include an additional feedstocksolution for providing additional oxygenated hydrocarbons for thehydrogenation reaction. The feedstock may include any one or moreoxygenated hydrocarbons listed above, including any one or more sugaralcohols, glucose, polyols, glycerol or saccharides. For instance, thesupplemental material may include glycerol. In this embodiment, crudeglycerol is used to initiate the reaction and to produce hydrogen so asto avoid polluting the hydrogenation catalyst with contaminants from thecrude glycerol. Purified glycerol is then added to the feedstocksolution prior to or at the same time the original feedstock solution isplaced in contact with the hydrogenation catalyst to increase theoxygenated hydrocarbons available for processing. It is anticipated thatthe opposite may be employed with the crude glycerol serving as thesupplement depending on the characteristics of the APR catalyst andhydrogenation catalyst.

In another embodiment, the supplement may include byproducts of thepresent invention recycled for further processing. The byproducts mayinclude diols, polyols, ketones, aldehydes, carboxylic acids, alcoholsand other products generated by the practice of the present invention.For example, the desired reaction product of one embodiment of thepresent invention is propylene glycol. However, the production ofpropylene glycol may also result in the production of other polyols,ketones, aldehydes, alcohols and carboxylic acids. The polyols may berecycled and added back into the feedstock solution prior to contactwith the hydrogenation catalysts in order to provide supplementaloxygenated hydrocarbons for conversion to propylene glycol. Similarily,ketones and alcohols may be added to the feedstock solution prior tocontact with the APR catalyst to further supplement the production ofhydrogen.

In yet another embodiment, the supplemental material may include acidsand salts. The addition of acidic compounds may provide increasedselectivity to the desired reaction products. In the preferredembodiments, the water-soluble acid may include, without limitation,nitrate, phosphate, sulfate, chloride salts, and mixtures thereof. If anoptional acidic modifier is used, it is preferred that it be present inan amount sufficient to lower the pH of the aqueous feed stream to avalue between about pH 1.0 and about pH 4.0. Lowering the pH of a feedstream in this manner may increase the proportion of diols, polyols,ketones, alcohols or alkanes in the final reaction products.

In another embodiment, the supplement may include additional hydrogenadded to the feedstock solution to supplement the APR hydrogen and tohelp drive the hydrogenation reaction to a desired reaction product. Theterm “supplemental hydrogen” refers to hydrogen that does not originatefrom within the feedstock, such as hydrogen added to the feedstock froman external source. For example, supplemental hydrogen may be added tothe system for purposes of increasing the reaction pressure over thehydrogenation catalyst, or to increase the molar ratio of hydrogen tocarbon and/or oxygen in order to enhance the production yield of certainreaction product types, such as ketones and alcohols. The supplementalhydrogen may be added at a molar ratio of supplemental hydrogen to APRhydrogen at amounts no greater than 1:1, and preferably no greater than1:3, and more preferably no greater than 1:10, and still more preferablyno greater than 1:20. In the most preferred embodiment, supplementalhydrogen is not added.

The amount of supplemental hydrogen to be added may also be calculatedby considering the concentration of oxygenated hydrocarbons in thefeedstock solution. Preferably, the amount of supplemental hydrogenadded should provide a molar ratio of oxygen atoms in the oxygenatedhydrocarbons to moles of hydrogen atoms (i.e., 2 oxygen atoms permolecule of H₂ gas) of less than or equal to 1.0. For example, where thefeedstock is an aqueous solution consisting of glycerol (3 oxygenatoms), the amount of supplemental hydrogen added to the feedstock ispreferably not more than about 1.5 moles of hydrogen gas (H₂) per moleof glycerol (C₃H₈O₃), and preferably not more than about 1.25, 1.0,0.75, 0.50 or 0.25. In general, the amount of supplemental hydrogenadded is preferably less than 0.75-times, and more preferably not morethan 0.67, 0.50, 0.33, 0.30, 0.25, 0.20, 0.15, 0.10, 0.05, 0.01-timesthe amount of total hydrogen (APR hydrogen and supplemental hydrogen)that would provide a 1:1 atomic ratio of oxygen to hydrogen atoms.

The amount of APR hydrogen within a reactor may be identified ordetected by any suitable method. The presence of APR hydrogen isdetermined based on the composition of the product stream as a functionof the composition of the feedstock stream, the catalyst composition(s)and the reaction conditions, independent of the actual reactionmechanism occurring within the feedstock stream. The amount of APRhydrogen may be calculated based on the catalyst, reaction conditions(e.g., flow rate, temperature, pressure) and the contents of thefeedstock and the reaction products. For example, the feedstock may becontacted with the APR catalyst (e.g., platinum) to produce APR hydrogenin situ and a first reaction product stream in the absence of ahydrogenation catalyst. The feedstock may also be contacted with boththe APR catalyst and the hydrogenation catalyst to produce a secondreaction product stream. By comparing the composition of the firstreaction product stream and the second reaction product stream atcomparable reaction conditions, one may identify the presence of APRhydrogen and calculate the amount of APR hydrogen produced. For example,an increase in the amount of oxygenated compounds with greater degreesof hydrogenation in the reaction product compared to the feedstockcomponents may indicate the presence of APR hydrogen.

Reaction Products

The present invention provides new methods for generating polyols,diols, ketones, aldehydes, carboxylic acids and alcohols in a singlecatalytic process using in-situ generated hydrogen. The polyols include,without limitation, diols, triols, 1,1,1tris(hydroxymethyl)-ethane(trimethylolethane), sorbitol and mannitol. The diols include, withoutlimitation, ethylene glycol, propylene glycol, butylene glycol,pentylene glycol, hexylene glycol, heptylene glycol, octylene glycol,nonylene glycol and decylene glycol. The triols include, withoutlimitation, glycerol (glycerin), trimethylolpropane, hexanetriol,2-ethyl-2-(hydroxymethyl)-1,3-propanediol (trimethylolpropane). Theketones include, without limitation, acetone, propan-2-one,2-oxopropanal, butan-2-one, butane-2,3-dione, 2-hydroxypropanal,3-hydroxybutan-2-one, pentan-2-one, pentane-2,3-dione,pentane-2,4-dione, hexan-2-one, heptan-2-one, octan-2-one, nonan-2-one,decan-2-one, and isomers thereof. The carboxylic acids include, withoutlimitation, lactic acid, butanoic acid, pentanoic acid, hexanoic acid,heptanoic acid, and isomers and derivatives thereof, includinghydroxylated derivatives such as 2-hydroxybutanoic acid. The aldehydesmay include, without limitation, acetaldehyde, prionaldehyde,butyraldehyde, pentanal, hexanal, heptanal, octanal, nonal, decanal, andisomers thereof. The alcohols include, without limitation, methanol,ethanol, propyl alcohol, isopropyl alcohol, propanol, butyl alcohol,isobutyl alcohol, butanol, pentanol, hexanol, heptanol.

The specific reaction products produced by the practice of the presentinvention will depend on various factors, including, without limitation,the feedstock solution, water concentration, reaction temperature,reaction pressure, the reactivity of the catalysts, and the flow rate ofthe feedstock solution as it affects the space velocity (the mass/volumeof reactant per unit of catalyst per unit of time), gas hourly spacevelocity (GHSV), and weight hourly space velocity (WHSV).

Preferably, the feedstock and reaction stream are contacted with thefirst catalyst material and the second catalyst material, respectively,at a weight hourly space velocity (WHSV) that is high enough to producea reaction product comprising one or more oxygenated hydrocarbons. It isbelieved that decreasing the WHSV below about 0.5 grams of theoxygenated hydrocarbons in the feedstock per hour may increase theamount of hydrocarbons in the reaction products. Therefore, the WHSV ispreferably at least about 1.0 grams of the oxygenated hydrocarbons inthe feedstock per hour, more preferably the WHSV is about 1.0 to 5.0 g/ghr, including a WHSV of about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7,1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1,3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4,5,4.6, 4.7, 4.8, 4.9 and 5.0 g/g hr. In one aspect, the feedstockcomprises glycerol contacted with a first catalytic material at a WHSVof about 1.9 or 4.0 g glycerol/hour to produce a reaction productcontaining propylene glycol.

One skilled in the art will appreciate that varying the factors above,as well as others, will generally result in a modification to thereaction product yield. For example, an increase in flow rate, andthereby a reduction of feedstock exposure to the catalyst over time,will likely result in a decrease in the amount of hydrogen available forhydrogenation over the hydrogenation catalyst. An increase in flow ratemay also limit the amount of time for hydrogenation to occur, therebycausing increased yield for higher level diols and polyols, with areduction in ketone and alcohol yields.

One skilled in the art may also modify the conditions above to enhancethe efficiency of the system and improve the costs for manufacturing thedesired reaction products. For example, modification of the water tooxygenated hydrocarbon ratio in the feedstock solution may improve theoverall thermal efficiency of the process by limiting the need forexternal temperature controls. The process is thermally efficient if theprocess is run at feed concentration of greater than 20% by weightoxygenated compound, preferably greater than 30 wt %, more preferablygreater than 40 wt % and most preferably greater than 50 wt %.

In one preferred embodiment, the present invention provides a method forproducing a polyol from an aqueous feedstock solution comprisingglycerol. FIG. 2 shows the reaction schematic for the generation ofpropylene glycol from glycerol with in-situ hydrogen generation. In thereaction scheme of FIG. 2, a portion of the glycerol is reacted withwater under aqueous-phase reforming conditions to generate APR hydrogenand carbon dioxide byproduct (Pathway 1 in FIG. 2). The stoichiometryfor Pathway 1 is shown in reaction 5 below:

C₃H₈O₃ [glycerol]+3H₂O→3CO₂+7 H₂  (5)

The generated APR hydrogen is then utilized for thedehydration/hydrogenation reaction (Pathway 2 in FIG. 2) for theselective generation of propylene glycol. The stoichiometry for Pathway2 is shown in reaction 6 below:

C₃H₈O₃ [glycerol]+H₂→C₃H₈O₂ [propylene glycol]+H₂O  (6)

In this step, a portion of the glycerol in the feedstock solution iscontacted with a portion of the APR hydrogen over a hydrogenationcatalyst under suitable aqueous phase reforming conditions to producethe polyols, such as ethylene glycol and propylene glycol. In thepreferred embodiment, the combination of the two reaction pathwaysoccurs according to the overall reaction shown in reaction 7.

1.14C₃H₈O₃→C₃H₈O₂+0.43CO₂+0.57H₂O  (7)

From this theoretical stoichiometry, 0.14 molecules of glycerol must bereformed to generate enough APR hydrogen to hydrogenate one molecule ofglycerol to propylene glycol.

In another embodiment, the present invention provides a method forproducing an alcohol from an aqueous feedstock solution comprisingglycerol. FIG. 3 provides a schematic illustration showing a process forconverting glycerol to an alcohol with in-situ hydrogen generation. Inthis process, glycerol is simultaneously (i.e., Steps 1 and 2 performedconcurrently over a single reactor bed) converted to APR hydrogen and analcohol (and other APR reaction products such carbon monoxide, carbondioxide, propylene glycol, methane, ethane, propane). The stoichiometryfor Pathway 1 is shown in reaction 8 below:

C₃H₈O₃ [glycerol]+3H₂O→3CO₂+7 H₂  (8)

The stoichiometry for Pathway 2 is shown in reaction 9 below:

C₃H₈O₃ [glycerol]+2H₂→C₃H₈O [propyl alcohol]+2H₂O  (9)

The overall reaction stoichiometry to generate 1 molecule of propylalcohol is shown in reaction 10 below:

1.28C₃H₈O₃ [glycerol]→C₃H₈O [propyl alcohol]+0.86 CO₂+1.14 H₂O  (10)

From this theoretical stoichiometry, 0.28 molecules of glycerol must bereformed to generate enough APR hydrogen to hydrogenate one molecule ofglycerol to propyl alcohol.

In yet another embodiment, methods for producing an alcohol from anaqueous feedstock solution comprising sorbitol are provided. FIG. 4 alsoprovides a schematic illustration showing a process for convertingsorbitol to an alcohol with in-situ hydrogen generation. In thisprocess, sorbitol is converted simultaneously (i.e., Steps 1 and 2performed concurrently over a single reactor bed) to hydrogen and analcohol (and other APR reaction products such as carbon monoxide, carbondioxide, methane, ethane, propane, butane, pentane, and hexane). Thestoichiometry for Pathway 1 is shown in reaction 11 below:

C₆H₁₄O₆ [sorbitol]+6H₂O→6CO₂+13 H₂  (11)

The stoichiometry for Pathway 2 is shown in reaction 12 below:

C₆H₁₄O₆ [sorbitol]+5H₂→C₆H₁₄O [hexanol]+5H₂O  (12)

The overall reaction stoichiometry to generate 1 molecule of hexanol isshown in reaction 13 below:

1.38C₆H₁₄O₆ [sorbitol]→C₆H₁₄O [hexanol]₊2.30CO₂+2.69 H₂O  (13)

From this theoretical stoichiometry, 0.38 molecules of sorbitol isreformed to generate enough APR hydrogen to hydrogenate one molecule ofsorbitol to hexanol.

One preferred method of generating an oxygenated compound comprises thesteps of: contacting a first catalytic material comprising one or moreGroup VIII metals with a first portion of an aqueous feedstock solutioncomprising water and at least one water soluble oxygenated hydrocarbonhaving two or more carbon atoms, at: a temperature of about 80° C. to400° C.; a weight hourly space velocity of at least about 1.0 gram ofthe oxygenated hydrocarbon per gram of the first catalytic material perhour; and a pressure where the water and the oxygenated hydrocarbons arecondensed liquids, to produce aqueous phase reforming (APR) hydrogen;and reacting the APR hydrogen with a second portion of the feedstocksolution over a second catalytic material, the second catalytic materialdifferent than the first catalytic material and selected from the groupconsisting of: iron, ruthenium, copper, rhenium, cobalt, nickel, alloysthereof, and mixtures thereof, at: a temperature of about 100° C. to300° C.; and a pressure of about 200 psig to about 1200 psig, to producea reaction product comprising one or more oxygenated compounds selectedfrom the group consisting of a polyol, a diol, a ketone, an aldehyde, acarboxylic acid and an alcohol. In one aspect, the first portion of thefeedstock solution and/or the second portion of the feedstock solutionare contacted with the first catalytic material and the second catalyticmaterial in a reactor vessel at a temperature of about 200° C. to 270°C., including 210° C., 220° C., 230° C., 240° C., 250° C., 260° C. andintervals of 1° C. between 200° C. and 270° C. In another aspect, thesecond portion of the feedstock solution is contacted with the APRhydrogen and the second catalytic material at a pressure greater thanabout 365 psig (e.g., 365-1,200 psig), preferably greater than 400 psig(e.g., 478 psig or 400-1,200 psig) or greater than 500 psig (e.g., 585psig or 500-1,200 psig). The feedstock is preferably passed through areactor at a weight hourly space velocity (WHSV) selected to provide aproduct stream comprising one or more oxygenated compounds, including atleast one of: a polyol, a ketone, an aldehyde, a carboxylic acid, and analcohol. For example the WHSV may be about 1.0 to 5.0 grams (including1.0-4.0, 1.0-3.0, 1.0-2.0, 2.0-5.0, 3.0-5.0, 4.0-5.0 and any otherinterval of 0.1 therebetween) of the oxygenated hydrocarbon(s) in thefeedstock per gram of the catalytic mixture per hour.

Another preferred method of generating propylene glycol comprises thestep of contacting a heterogeneous catalyst system comprising one ormore Group VIII metals (e.g., one or more metals including platinum) anda hydrogenation catalyst with an aqueous feedstock solution comprisingwater and a water-soluble oxygenated hydrocarbon (e.g., glycerol orsorbitol) at a temperature and pressure suitable to maintain thefeedstock in a liquid phase at (e.g., including temperatures of about100° C. to 300° C.) at a weight hourly space velocity of at least about1.0 gram of the water-soluble oxygenated hydrocarbon per gram of theheterogeneous catalyst per hour and a pressure where the feedstockremains a condensed liquid to produce a reaction product comprising oneor more oxygenated compounds, such as a polyol (e.g., propylene glycol),an aldehyde, a ketone, a carboxylic acid (e.g., lactic acid) and/or analcohol. The heterogeneous catalyst system may include a first catalystmaterial containing a Group VIII metal or any suitable APR catalyst, anda second catalyst containing a hydrogenation catalyst. The heterogeneouscatalyst system may be a catalytic mixture of the Group VIII metal andthe hydrogenation catalyst. The heterogeneous catalyst system may alsobe two separate catalytic materials, including an APR catalyst and ahydrogenation catalyst, contacted separately or together with thefeedstock. Preferably the heterogeneous catalyst system includes thefirst catalytic material (e.g., an APR catalyst containing at least oneGroup VIII metal) and the second catalytic material (e.g., ahydrogenation catalyst) in a molar ratio of 5:1 to 1:5, including ratiosof 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4 and ratio intervals of 0.1 between5:1 and 1:5.

In certain aspects of the preferred embodiments, the first catalyticmaterial comprises at least one transition metal selected from the groupconsisting of platinum, nickel, palladium, ruthenium, rhodium, rhenium,iridium, alloys thereof, and mixtures thereof. Alternatively, the firstcatalytic material may also be selected from one of more of thefollowing groups: platinum, nickel, palladium, ruthenium, rhodium,rhenium, iridium and mixtures thereof; platinum, nickel, palladium,ruthenium, rhodium, rhenium, iridium, and alloys thereof; platinum,nickel, palladium, ruthenium, rhodium, rhenium, iridium, alloys thereof,and mixtures thereof; platinum, nickel, palladium, ruthenium, rhodium,iridium, alloys thereof and mixtures thereof; platinum, nickel,palladium, rhenium, iridium, alloys thereof, and mixtures thereof;nickel, palladium, ruthenium, rhodium, rhenium, iridium, alloys thereof,and mixtures thereof; and nickel, palladium, ruthenium, rhodium,iridium, alloys thereof, and mixtures thereof.

In certain aspects of the preferred embodiments, the second catalyticmaterial is selected from one or more of the following groups: iron,nickel, ruthenium, and cobalt; iron, ruthenium, and cobalt; iron,nickel, and cobalt; iron, nickel, and ruthenium; nickel, ruthenium, andcobalt; iron, nickel and ruthenium; and iron and cobalt. Preferably, thesecond catalytic material is different from the first catalyticmaterial.

Optionally, the first catalytic material and/or the second catalyticmaterial may be adhered to one or more suitable support materials, suchas a support with Bronsted acid sites. The support may comprise carbon.Also optionally, the heterogeneous catalyst may consist essentially of(or consist of) about 5 wt % iron and platinum in a molar ratio of about1:1 on an activated carbon support; the feedstock may comprise at leastabout 20 wt % (including 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, andamounts of 1% therebetween) of one or more oxygenated hydrocarbon(s)such as glycerol and/or sorbitol; the feedstock may be contacted withthe heterogeneous catalyst at a weight hourly space velocity of about1.0 to 5.0 grams of glycerol per gram of the heterogeneous catalyst perhour and a pressure of about 250-600 psig (including 300-600 psig,300-1,200 psig, 365-600 psig, 365-1,200 psig, 400-600 psig, 478 psig,478-1,200 psig, 585 psig and 585-1,200 psig); or the reaction producthas a carbon yield of propylene glycol of 40% or greater (including 50%,60%, 70%, 80%, 90% or greater). The amount of propylene glycol in thereaction product is preferably at least about 5%, 10%, 20%, 30% or 40%of the amount of liquid reaction product.

When present, the amount of supplemental hydrogen is preferably providedsparingly. The feedstock is preferably substantially free ofsupplemental hydrogen throughout the reaction process. Most preferably,the amount of external supplemental hydrogen is provided in amounts thatprovide less than one hydrogen atom per oxygen atom in all of theoxygenated hydrocarbons in the feedstock stream prior to contacting acatalyst. For example, the molar ratio between the supplemental hydrogenand the total water-soluble oxygenated hydrocarbons in the feedstocksolution is preferably selected to provide no more than one hydrogenatom in the supplemental (external) hydrogen per oxygen atom in theoxygenated hydrocarbon. In generally, the molar ratio of the oxygenatedhydrocarbon(s) in the feedstock to the supplemental (external) hydrogenintroduced to the feedstock is preferably not more than 1:1, morepreferably up to 2:1, 3:1, 5:1, 10:1, 20:1 or greater (including 4:1,6:1, 7:1, 8:1, 9:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1 and19:1). The amount (moles) of hydrogen introduced to the feedstock froman external source is preferably 0-30%, 0-25%, 0-20%, 0-15%, 0-10%,0-5%, 0-2%, 0-1% of the total number of moles of the oxygenatedhydrocarbon(s) in the feedstock, including all intervals therebetween.Also preferably, when the feedstock solution or any portion thereof isreacted with APR hydrogen and an external hydrogen, the molar ratio ofAPR hydrogen to external hydrogen is at least 3:1, including ratios of5:1, 10:1, 20:1 and ratios therebetween (including 4:1, 6:1, 7:1, 8:1,9:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1 and 19:1).

In another embodiment, compositions of matter are provided. Thecomposition of matter may be found within a reactor system, includingwithin the reactor vessel and/or within a separator attached thereto.The composition of matter may comprise water, glycerol, carboxylic acid,carbon dioxide, propylene glycol, and a catalyst composition comprisinga first catalytic material and a second catalytic material as describedabove. Preferably, the catalyst composition includes a Group VIII metaland a hydrogen catalyst (e.g., platinum and iron).

In anther embodiment, reactor systems are provided. The reactor systemfor producing oxygenated compounds from a polyol may include: a firstreaction bed adapted to receive an aqueous feedstock solution comprisingwater and at least one water soluble oxygenated hydrocarbon having twoor more carbon atoms, the first reaction bed comprising a first catalystas described above configured to contact a first portion of thefeedstock solution in a condensed phase to form a reactant streamcomprising hydrogen; and a second reaction bed configured to receive thereactant stream from the first reaction bed, the second reaction bedcomprising a second catalytic material as described above, andconfigured to cause a reaction between the hydrogen and a second portionof the feedstock solution to produce a product stream comprising one ormore oxygenated compounds selected from the group consisting of a polyol(e.g., a diol), a ketone, an aldehyde, a carboxylic acid and an alcohol.

The following examples are included solely to provide a more completedisclosure of the subject invention. Thus, the following examples serveto illuminate the nature of the invention, but do not limit the scope ofthe invention disclosed and claimed herein in any fashion.

EXAMPLES Example 1 Illustrative Reactor System 1

FIG. 5 is a schematic illustration showing one preferred process forconverting a feedstock solution 1 to a final desired product 12 using asingle reactor containing a catalyst composed of a mixture of the APRcatalyst and hydrogenation catalyst. The feedstock solution 1 includeswater combined with one or more oxygenated hydrocarbons, such asglycerol or sugar alcohol. The feedstock solution 1 is combined with arecycle stream 15 containing unreacted polyols, water, and byproducts ofthe process, such as methanol and ethanol, from the process. Thecombined stream 2 is fed via an HPLC pump (not shown) to reactor system3 having the APR/hydrogenation catalyst, where a portion of the streamreacts with water over the catalyst to form APR hydrogen, whichsubsequently reacts with the other portion of the stream over thehydrogenation catalyst to generate the desired products.

The effluent stream 4 from the reactor 3 contains a mixture of water,hydrogen, carbon dioxide, light hydrocarbons, light alcohols (methanoland ethanol), diol product and unreacted glycerol. The mixture is cooledand separated in a two-phase separator 5 where the non-condensed gases(such as hydrogen, carbon dioxide, methane, ethane and propane) areremoved via stream 6 from the phase containing the water solublealcohols and diols. The non-condensable stream 6 can be either combustedto create process heat (i.e., heat for driving the reaction in reactor3) or sent to a separation system where hydrogen can be recovered forrecycle back to stream 2. The aqueous stream 7 may be sent to aseparator 8 where the light alcohols (methanol and ethanol) and waterare removed and recycled back via stream 10 to the reactor inlet. Apurge stream 14 is included to prevent a build-up of water in thereactor system.

A crude product stream 9, containing unreacted glycerol and desiredpolyol, diol, ketone, aldehyde, carboxylic acid and/or alcohol products,is recovered from separator 8 via stream 9 and sent to a finishingseparator where the desired product 12 is separated from unreactedglycerol 13. The unreacted glycerol stream is then added to stream 10and recycled back to the reactor system via stream 15.

Example 2 Illustrative Reactor System 2

FIG. 6 is a schematic showing another preferred process for converting apolyol feedstock solution 101 to a final diol product 114 using areactor system that includes a first reactor bed 103 having an APRcatalyst and a second reactor bed 104 having a hydrogenation catalyst.The feedstock solution 101 includes water combined with one or moreoxygenated hydrocarbons, such as sugar alcohol or glycerol. Feedstocksolution 101 is combined with a recycle stream 117 containing unreactedpolyols, water, and underdesirable byproducts (e.g., methanol andethanol). The combined stream 102 is fed via an HPLC pump (not shown) tofirst reactor bed 103 where a portion of the stream reacts with waterover the APR catalyst to form APR hydrogen. The recycled alcohols(methanol and ethanol) also react with water over the APR catalyst toform APR hydrogen and light hydrocarbons, such as methane and ethane.

Effluent containing APR hydrogen, water, CO₂, light hydrocarbons andpolyols move from first reactor bed 103 to second reactor bed 104 wherethe APR hydrogen reacts with a portion of the polyols to generate thedesired products. In this illustration, the reactor bed 103 and reactorbed 104 are set in an up-flow orientation to allow the generated APRhydrogen to percolate from reactor bed 103 through second reactor bed104 to maximize the interaction of APR hydrogen and stream 102 over thehydrogenation catalyst. Reactor beds 103 and 104 may also be designed toaccommodate down-flow or horizontal-flow orientations.

The effluent stream 105 from the reactor system contains a mixture ofwater, hydrogen, carbon dioxide, light hydrocarbons, light alcohols(methanol and ethanol), diol and polyol products, and unreactedglycerol. The mixture is cooled and separated in a two-phase separator106 where the non-condensable gases (such as hydrogen, carbon dioxide,methane, ethane and propane) are removed via stream 107 from the phasecontaining the water soluble alcohols, diols and polyols. Thenon-condensable stream 107 can be either combusted to create processheat or sent to a separation system where hydrogen is recovered forpossible recycle back to stream 102. The aqueous stream 108 is sent to aseparator 109 where the light alcohols (methanol and ethanol) and waterare removed and recycled back via stream 110 to the reactor inlet. Apurge stream 116 is included to prevent a build-up of water in thereactor system.

A crude product stream 112, containing unreacted glycerol and thedesired polyol, diol and/or alcohol products, is recovered fromseparator 109 via stream 112 and sent to a finishing separator 113 wherethe desired product 114 is separated from unreacted glycerol 115. Theunreacted glycerol stream is added to stream 110 and recycled back tothe reactor system via stream 117.

Example 3 Illustrative Reactor System 3

FIG. 7 is a schematic showing another preferred process for converting afeedstock solution 201 to a final product 215 with the introduction of asupplement 205. Supplement 205 may include various salts, acids,additional feedstock solution, hydrogen or byproducts of the process.

Feedstock solution 201 includes water combined with one or moreoxygenated hydrocarbons, such as glycerol or sugar alcohol. Feedstocksolution 201 may contain the same combination as feedstock solution 205or a combination of one or more low cost oxygenated compounds, such aswaste methanol from a biodiesel process, ethylene glycol from spentantifreeze, or low cost alcohols. Stream 201 may also be combined withrecycle stream 218, which contains unreacted polyols, water andunderdesirable byproducts, such as methanol and ethanol, to formcombined stream 202.

Combined stream 202 is fed via an HPLC pump (not shown) to reactor bed203 having an APR catalyst. Oxygenated hydrocarbons in combined stream202 react with water over the APR catalyst to form APR hydrogen, whilethe recycled alcohols (i.e., methanol and ethanol) form hydrogen andlight hydrocarbons, such as methane and ethane.

Effluent from first reactor bed 204, containing APR hydrogen, water,CO₂, light hydrocarbons, and unreacted hydrocarbons, is combined withsupplement 205. In this illustration, supplement 205 is a feedstocksolution containing a higher grade of oxygenated hydrocarbons, such aspurified glycerol. The combined effluent 204 and supplement 205 aredirected to reactor bed 206 that includes a hydrogenation catalyst forreacting the APR hydrogen with the oxygenated hydrocarbons to generatethe desired polyol, diol and/or alcohol product 215. Effluent stream 207from the reactor contains a mixture of water, hydrogen, carbon dioxide,light hydrocarbons, light alcohols (methanol and ethanol), polyols,diols, ketones, aldehydes, carboxylic acids and unreacted glycerol.

The mixture is cooled and separated in a two-phase separator 208 wherethe non-condensable gases, such as hydrogen, carbon dioxide, methane,ethane and propane, are removed via stream 209 from the phase containingwater-soluble polyols, alcohols and/or diols. The stream 209 can beeither combusted to create process heat or sent to a separation systemwhere hydrogen can be recovered for possible recycle back to stream 201or used as a supplement 205.

Aqueous stream 210 is sent to a separator 211 where the light alcohols(methanol and ethanol) and water are removed and recycled back viastream 212 to the reactor inlet. A purge stream 217 is included toprevent a build-up of water in the reactor system. A crude productstream 213 containing the desired product 215 and unreacted hydrocarbonsis recovered from separator 211 via stream 213 and sent to a finishingseparator 214 where the desired product 215 is separated from theunreacted hydrocarbons 216. The unreacted hydrocarbon stream is added tostream 216 and recycled back to the reactor system via stream 218 orused as supplement 205.

Example 4 Illustrative Reactor System 4

The generation of polyols from glycerol is performed using the testsystem illustrated in FIG. 8. The reactor in the system is configured ina down flow orientation which improves contact of the aqueous feedstocksolutions with in-situ generated APR hydrogen as it flows through thereactor.

Catalysts are loaded into a stainless steel tube reactor 1, which isinstalled in an aluminum block heater 2 to maintain isothermalconditions. The reaction temperature is controlled by the temperaturecontrol subsystem. Some components of the temperature control subsystem(not shown in FIG. 8) include a thermocouple inserted into the tubereactor, resistive heaters mounted on the aluminum block, and a PIDcontroller.

Substrate solutions (i.e., feedstock solutions) can be selected to becontinuously fed into the reactor using an HPLC pump 3. The materialexiting the reactor is cooled as it passes through heat exchanger 4before entering the phase separator 5.

Gasses exit the phase separator via the gas manifold 6, which ismaintained at constant pressure by the pressure control subsystem.Components of the pressure control subsystem include: the pressuresensor 7, pressure control valve 8, and PID controller 9. The quantityof gas released by the pressure control valve 8 is measured by mass flowmeter 10. The composition of this gas is monitored by gaschromatography.

The liquid level in phase separator 5 is maintained at constant level bythe level control subsystem. The components of the level controlsubsystem include the level sensor 11 in the phase separator, a levelcontrol valve 12 and PID controller 13. The aqueous solution drainedfrom the phase separator during a catalyst evaluation experiment iscollected and the quantity collected measured gravimetrically. Analysisof this solution may include, pH, total organic carbon concentration, GCto determine the concentrations of unreacted substrate and specificintermediates and side products.

Example 5 Preparation of Improved Carbon Support

Hydrogen peroxide was used to functionalize activated carbons to provideimproved supports for catalysts. See S. R. de Miguel, O. A. Scelza, M.C. Roman-Martinez, C. Salinas Martinez de Lecea, D. Cazorla-Amoros, A.Linares-Solano, Applied Catalysis A: General 170 (1998) 93. Activatedcarbon, 61 g, was added slowly to 1600 ml of 30% hydrogen peroxidesolution. After the addition of carbon was complete, the mixture wasleft overnight. The aqueous phase was decanted and the carbon washedthree times with 1600 mL of DI water, then dried under vacuum at 100° C.

Example 6 Preparation of a Bimetallic Catalyst System

A bimetallic catalyst system containing a 5 wt % platinum (APR catalyst)and iron (hydrogenation catalyst) mixture (molar ratio 1:1) supported onactivated carbon was prepared using incipient wetness techniques. Anaqueous solution, with a volume equal to incipient wetness volume forthe carbon to be impregnated, 10.4 mL, and containing 1.72 g ofdihydrogen hexachloroplatinate (IV) hexahydrate (Alfa Aesar, 39.85% Pt)and 1.42 g of iron(III) nitrate nonahydrate (Alfa Aesar) was applieddropwise, while stirring, to 13.02 g of hydrogen peroxide functionalizedcarbon (Example 5). The wetted carbon was dried at 100° C. under vacuum.

Example 7 Propylene Glycol Production

The catalyst system described in Example 6 was tested in the apparatusdescribed in Example 4 using a feedstock solution containing 50 wt %glycerol. Prior to introducing the glycerol feedstock solution, thecatalyst was treated under flowing hydrogen at 350° C. The reactionconditions were set at 240° C., 33.0 bar (478 psig), and WHSV of 4.0grams glycerol per gram of catalyst per hour. The glycerol conversionwas 64%. This experiment was repeated with a second feedstock solutioncontaining 50 wt % glycerol and 50% water feed over the catalyst ofExample 6 the following reaction conditions: 260° C., 40.3 bar (585psig), WHSV of 1.9 grams glycerol per gram of catalyst per hour.

At the low temperature regime, pressures and catalyst amounts used wereall commercially viable conditions for the APR process. The glycerolconversions for these two cases were 64% and 88% of the theoreticalmaximum, respectively. FIG. 9 summarizes the yield of carbon containingproducts, and shows the selectivity of the conversion of glycerol to thecarbon-containing products for the high and low temperature reactions.The graph shows that propylene glycol was the major product generated,followed by carbon dioxide (a byproduct of the in-situ generation of APRhydrogen), ethanol, and ethylene glycol. The gas phase alkanes includedmethane, ethane, and propane, with methane being the most abundantgas-phase alkane.

The results confirm that it is possible to generate propylene glycol inreasonable yields via liquid-phase reforming of aqueous solutions ofglycerol, and that it is possible to generate significant or predominantamounts of propylene glycol from glycerol with in-situ generatedhydrogen and, preferably, without concurrently introducing hydrogen froman external source. The presence of byproducts from the hydrogengeneration process surprisingly did not significantly impact the abilityof the glycerol conversion to propylene glycol and other products.

The described embodiments and examples are to be considered in allrespects only as illustrative and not restrictive, and the scope of theinvention is, therefore, indicated by the appended claims rather than bythe foregoing description. All changes which come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

1. A method of generating ketones or alcohols, the method comprising thesteps of: a. contacting a first catalytic material comprising one ormore Group VIII metals with a first portion of an aqueous feedstocksolution comprising water and at least one water-soluble oxygenatedhydrocarbon having two or more carbon atoms under conditions sufficientto produce hydrogen; and b. reacting the hydrogen with a second portionof the aqueous feedstock solution over a second catalytic material, thesecond catalytic material different than the first catalytic materialand comprising iron, ruthenium, copper, rhenium, cobalt, nickel, analloy of at least two of the foregoing, or mixtures of at least two ofthe foregoing, under conditions sufficient to produce one or moreketones selected from the group consisting of acetone, propanone,butanone, pentanone, and hexanone, or one or more alcohols selected fromthe group consisting of methanol, ethanol, iso-propyl alcohol, propanol,butanol, pentanol, and hexanol.
 2. The method of claim 1 furthercomprising the step of adding a supplemental hydrogen to react with atleast a portion of the second portion of the aqueous feedstock solution.3. The method of claim 1, wherein the first catalytic material contactsthe first portion of the aqueous feedstock at: a. a temperature of about80° C. to 400° C.; and b. a pressure where at least a portion of thewater and the oxygenated hydrocarbons are condensed liquids.
 4. Themethod of claim 1, wherein the hydrogen reacts with a second portion ofthe feedstock solution at: a. a temperature of about 100° C. to 300° C.;and b. a pressure of about 72 psig to about 1300 psig.
 5. The method ofclaim 1, wherein the second portion of the feedstock solution furthercomprises oxygenated hydrocarbons formed by contacting the feedstocksolution with the first catalytic material.
 6. The method of claim 1,wherein the second portion of the feedstock solution is contacted withthe hydrogen and the second catalytic material at a pressure greaterthan about 365 psig.
 7. The method of claim 1, wherein the molar ratioof the first catalytic material to the second catalytic material isabout 5:1 to 1:5.
 8. The method of claim 1, wherein the first catalyticmaterial comprises at least one transition metal selected from the groupconsisting of platinum, nickel, palladium, ruthenium, rhodium, rhenium,iridium, an alloy of at least two of the foregoing, and mixtures of atleast two of the foregoing.
 9. The method of claim 1, wherein the secondcatalytic material is selected from the group consisting of iron,nickel, rhenium, ruthenium, and cobalt.
 10. The method of claim 1,wherein the first catalytic material and the second catalytic materialare combined in a catalytic mixture.
 11. The method of claim 10, whereinthe first catalytic material comprises at least one transition metalselected from the group consisting of: platinum, nickel, palladium,ruthenium, rhodium, rhenium, iridium, an alloy of at least two of theforegoing and mixtures of at least two of the foregoing; and the secondcatalytic metal is iron or rhenium.
 12. The method of claim 11, whereinthe first catalytic material is platinum and the second catalyticmaterial is rhenium.
 13. The method of claim 10, wherein the firstportion of the feedstock solution and the second portion of thefeedstock solution are contacted with the first catalytic material andthe second catalytic material in a reactor vessel at a temperature ofabout 200° C. to 270° C.
 14. The method of claim 10, wherein thecatalytic mixture is adhered to a support.
 15. The method of claim 14,wherein the support is selected from the group consisting of carbon,silica, silica-alumina, alumina, zirconia, titania, ceria, vanadia, andmixtures thereof.
 16. The method of claim 15, wherein the support is anactivated carbon.
 17. The method of claim 15, wherein the supportcomprises zirconia.
 18. The method of claim 1, wherein the first portionof the feedstock solution is contacted with the first catalytic materialat a temperature of about 150° C. to 270° C. and the second portion ofthe feedstock solution is contacted with the second catalytic materialat a temperature of about 200° C. to 270° C.
 19. A method of generatingketones or alcohols, the method comprising the steps of: a. contacting afirst catalytic material comprising one or more Group VIII metals with afirst portion of an aqueous feedstock solution comprising water, arecycle stream and at least one water-soluble oxygenated hydrocarbonhaving two or more carbon atoms under conditions sufficient to producehydrogen; and b. reacting the hydrogen with a second portion of theaqueous feedstock solution over a second catalytic material, the secondcatalytic material different than the first catalytic material andselected from the group consisting of: iron, ruthenium, copper, rhenium,cobalt, nickel, an alloy of at least two of the foregoing, and mixturesof at least two of the foregoing, under conditions sufficient to producean effluent stream comprising unreacted oxygenated hydrocarbons,byproducts and one or more ketones selected from the group consisting ofacetone, propanone, butanone, pentanone, and hexanone, or one or morealcohols selected from the group consisting of methanol, ethanol,iso-propyl alcohol, propanol, butanol, pentanol, and hexanol; and c.separating at least a portion of the unreacted oxygenated hydrocarbonsand byproducts from the effluent stream into the recycle stream; and d.mixing at least a portion of the recycle stream with one or morewater-soluble oxygenated hydrocarbons to provide the aqueous feedstocksolution.
 20. The method of claim 19 further comprising the step ofadding a supplemental hydrogen to react with at least a portion of thesecond portion of the aqueous feedstock solution.
 21. The method ofclaim 19, wherein the first catalytic material contacts the firstportion of the aqueous feedstock at: a. a temperature of about 80° C. to400° C.; and b. a pressure where at least a portion of the water and theoxygenated hydrocarbons are condensed liquids.
 22. The method of claim19, wherein the hydrogen reacts with a second portion of the feedstocksolution at: a. a temperature of about 100° C. to 300° C.; and b. apressure of about 72 psig to about 1300 psig.
 23. The method of claim19, wherein the second portion of the feedstock solution is contactedwith the hydrogen and the second catalytic material at a pressuregreater than about 365 psig.
 24. The method of claim 19, wherein themolar ratio of the first catalytic material to the second catalyticmaterial is about 5:1 to 1:5.
 25. The method of claim 19, wherein thefirst catalytic material comprises at least one transition metalselected from the group consisting of platinum, nickel, palladium,ruthenium, rhodium, rhenium, iridium, an alloy of at least two of theforegoing, and mixtures of at least two of the foregoing.
 26. The methodof claim 19, wherein the second catalytic material is selected from thegroup consisting of iron, nickel, rhenium, ruthenium, and cobalt. 27.The method of claim 19, wherein the first catalytic material and thesecond catalytic material are combined in a catalytic mixture.
 28. Themethod of claim 27, wherein the first catalytic material comprises atleast one transition metal selected from the group consisting of:platinum, nickel, palladium, ruthenium, rhodium, rhenium, iridium, analloy of at least two of the foregoing and mixtures of at least two ofthe foregoing; and the second catalytic metal is iron or rhenium. 29.The method of claim 27, wherein the first catalytic material is platinumand the second catalytic material is rhenium.
 30. The method of claim27, wherein the first catalytic material and the second catalyticmaterial are adhered to a support.
 31. The method of claim 30, whereinthe support is selected from the group consisting of carbon, silica,silica-alumina, alumina, zirconia, titania, ceria, vanadia, and mixturesthereof.
 32. The method of claim 31, wherein the support is an activatedcarbon.
 33. The method of claim 31, wherein the support compriseszirconia.
 34. The method of claim 19, wherein the first portion of thefeedstock solution is contacted with the first catalytic material at atemperature of about 150° C. to 270° C. and the second portion of thefeedstock solution is contacted with the second catalytic material at atemperature of about 200° C. to 270° C.
 35. A method of generatingketones or alcohols, the method comprising the steps of: a. contacting afirst catalytic material comprising one or more Group VIII metals with afirst portion of an aqueous feedstock solution comprising water and atleast one water-soluble oxygenated hydrocarbon having two or more carbonatoms under conditions sufficient to produce aqueous phase reforming(APR) hydrogen; and b. reacting the APR hydrogen and a supplementalhydrogen with a second portion of the aqueous feedstock solution over asecond catalytic material, the second catalytic material different thanthe first catalytic material and comprising iron, ruthenium, copper,rhenium, cobalt, nickel, an alloy of at least two of the foregoing, ormixtures of at least two of the foregoing, under conditions sufficientto produce one or more ketones selected from the group consisting ofacetone, propanone, butanone, pentanone, and hexanone, or one or morealcohols selected from the group consisting of methanol, ethanol,iso-propyl alcohol, propanol, butanol, pentanol, and hexanol.
 36. Themethod of claim 35, wherein the first catalytic material contacts thefirst portion of the aqueous feedstock at: a. a temperature of about 80°C. to 400° C.; and b. a pressure where at least a portion of the waterand the oxygenated hydrocarbons are condensed liquids.
 37. The method ofclaim 35, wherein the APR hydrogen and the supplemental hydrogen reactwith a second portion of the feedstock solution at: a. a temperature ofabout 100° C. to 300° C.; and b. a pressure of about 72 psig to about1300 psig.
 38. The method of claim 35, wherein the second portion of thefeedstock solution is contacted with the APR hydrogen, the supplementalhydrogen and the second catalytic material at a pressure greater thanabout 365 psig.
 39. The method of claim 35, wherein the molar ratio ofthe first catalytic material to the second catalytic material is about5:1 to 1:5.
 40. The method of claim 35, wherein the first catalyticmaterial comprises at least one transition metal selected from the groupconsisting of platinum, nickel, palladium, ruthenium, rhodium, rhenium,iridium, an alloy of at least two of the foregoing, and mixtures of atleast two of the foregoing.
 41. The method of claim 35, wherein thesecond catalytic material is selected from the group consisting of iron,nickel, rhenium, ruthenium, and cobalt.
 42. The method of claim 35,wherein the first catalytic material and the second catalytic materialare combined in a catalytic mixture.
 43. The method of claim 42, whereinthe first catalytic material and second catalytic material are adheredto a support.
 44. The method of claim 43, wherein the support isselected from the group consisting of carbon, silica, silica-alumina,alumina, zirconia, titania, ceria, vanadia, and mixtures thereof.